This invention relates to a method for preparing novel polymeric acetal carboxylates useful as complexing agents and detergency builders.
The property possessed by some materials of improving detergency levels of soaps and synthetic detergents and the use of such materials in detergent compositions is known. Such cleaning boosters are called "builders" and such builders permit the attainment of better cleaning performance than is possible when so-called unbuilt compositions are used. The behavior and mechanisms by which builders perform their function are only partially understood. It is known that good builders must be able to sequester most of the calcium and/or magnesium ions in the wash water since these ions are detrimental to the detergency process. However, it is difficult to predict which class of compounds possess useful combinations of builder properties and which compounds do not because of the complex nature of detergency and the countless factors which contribute both to overall performance results and the requirements of environmental acceptability.
Sodium tripolyphosphate (STP) has been found to be a highly efficient cleaning and detergent builder and this compound has been widely used for decades in cleaning and detergent formulations. Indeed, millions of pounds of STP are used each year in cleansing formulations because of its superior builder qualities. However, because of the recent emphasis on removing phosphates from detergent and cleaning compositions for environmental reasons, the detergent and cleaning industry is now looking for materials suitable for use as builders which do not contain phosphorus, and which are environmentally acceptable.
A large number of materials which do not contain phosphorus have been evaluated for use in detergent and cleaning formulations as a builder, but all of these materials suffer one or more disadvantages, usually either poor builder properties or poor biodegradability. As an example, U.S. Pat. No. 3,692,685 discloses salts of oxydisuccinic acid and carboxymethyl oxysuccinic acid as detergent builders and U.S. Pat. No. 3,708,436 discloses a mixture of polymeric maleic anhydride with sodium nitrilotriacetate or STP. Numerous U.S. Patents, such as U.S. Pat. No. 3,704,320, disclose ether carboxylates as detergency builders and several references, such as U.S. Pat. No. 3,764,586 and U.S. Pat. No. 3,308,067, disclose polymeric, aliphatic polycarboxylic acids having certain specific structural relationships useful as builders.
Despite the advances taught in these and other references in the prior art to find a cleaning and detergency builder which does not contain phosphorus, all of these materials suffer from one or more disadvantages. Of the above-mentioned materials, those that are biodegradable are not equivalent to STP in builder performance, and of those that are equivalent to STP in builder performance, they are usually biodegradable only with great difficulty. Inorganic builders other than STP are generally not satisfactory for use as a builder in detergent formulations because of their poor builder properties. Sodium aluminum silicates, commonly known as zeolites, have been proposed for use in detergent formulations since they are able to soften water by removing calcium ions; however, they are not very effective in removing magnesium ions from water. Moreover, it is clear that such water-insoluble, clay-like materials have the potential problem of producing a sediment in the cleaning solution and the resulting waste waters. Thus, it can be seen that there is a need for a new class of materials with builder properties equivalent to STP, which does not contain phosphorus, which is water-soluble, and which achieve environmental acceptability by being readily biodegradable.
In copending application Ser. No. 826,424; application Ser. No. 826,425 and application Ser. No. 826,426 filed Aug. 22, 1977 by Crutchfield, Papanu and Warren, methods of preparing polyacetal carboxylates are described wherein an ester of glyoxylic acid is brought together with a polymerization initiator, and thereafter, the resulting polymer is stabilized against rapid depolymerization in alkaline solution. Although satisfactory results are obtained by the above procedure, the present invention provides a method in which the initiator stabilizes a portion of the chain ends of the resulting polymer against rapid depolymerization in alkaline solution.